Cutter grinder



May 31, 1938. J. B. ARMITAGE CUTTER GR I NDER Filed Oct. 29, 1 934 2Sheets-Sheet 1 Fig.1

INVETOR Gal May 31, 11938.

J. B. ARMITAGE CUTTER GRINDER Filed Oct. 29, 1934 2 Sheets-Sheet 2Patented May 3t, 1938 CUTTER GENDER Application hotelier 29, 19%, SerialNo. 7l5,4dil,

% illlainms.

This invention relates generally to machine tools and more particularlyto precision grinding machines.

It is an object of the invention to provide a grinding machine of a typeparticularly adapted for grinding milling cutters having improvedrigidity of support of the cutter to be ground and the grinding wheeland an improved rela.- tionship of supports for relative adjustment andfor relative grinding movement of the cutter and wheel. I v

A further object is to improve the mounting of the grinding wheel andits driving means, particularly in a manner to avoid or minimizedistortion or displacement which might disturb the desired relationship.of the grinding wheel andthe cutter during the grinding operation, andin a manner to avoid vibration or chatter.

Another object is to provide a driving transmission for the grindingwheel which will maintain a desired surface speed of the wheelsubstantially constant in spite of variations in load which occur as thewheel meets the cutter surface to be ground.

A further purpose is generally to simplify and improve the constructionand operation of cutter grinders and especially the wheel drivingmechanism and its associated elements, and still from the descriptionand claims herein.

The invention consists of the construction and combination of parts asherein illustrated and explained, and in such modification thereof asmay be equivalent to the structure set forth in and defined by theclaims.

The same reference characters have been used to designate the same partsthroughout the drawline ll-t of Fig. 1.

The cutter grinding machine comprises a base it upon which is mounted acutter supporting unit generally denoted by numeral 2, and a grindingwheel unit generally denoted by numeral 3.

Supporting unit 2 provides a. rotatable cutter carother' objects andadvantages will be apparent Fig. 4 is a view in cross section takenalong ('Ull. 51166) rying spindle t which at the one end is providedwith a hand wheel 5 for rotation thereof, and atthe other end isprovided with an exposed portion upon which the cutter to be ground ismounted for rotation coaxial with the spindle. Wheel unit 3 provides agrinding wheel spindle 6 upon which is mounted the rotor of an electricmotor generally denoted by the numeral I, and an abrasive grinding wheel8 fixed to the front end of spindle adjacent to the cutter support.

The cutter supporting unit 2 includes various relatively movablesupports as follows: Slidably guided on base II for reciprocatorymovement in a path transverse to the axis of wheel spindle 6 is asupport 9 upon which a support "I is mountedtobe adjustable angularlyabout a vertical axis. Support ill carriesa. support ill slidably guidedfor vertical adjustment, in which the cutter spindle t is rotatablymounted. Support 9 may be moved by the means of a. hand crank, notshown, applied to the squared end of screw 62 which engages a'. nut i3,and may be clamped in any position of adjustment by a clamp screw it.Support it may be rotated by the means of a crank, not shown, applied tothe squared end of a. shaft it, which turns a. worm it, enaging a wormwheel I! fixed on the lower end of the support as best shown in Fig. 4,and may be clamped in any, position of adjustment by the means ofT-bolts i8. Support may be adjusted vertically by the means of a handcrank, not shown, applied to the squared end of a screw 20, whichengages with a nut 20, and may be clamped in any position of adjustmentby the means of a T-bolt 22. The spindle t may be rotated, as previouslynoted, by the hand wheel 5. This serves to turn the cutter mounted at gthe other end of the spindle in a. step-by-step motion to present thedifferent teeth of the cutter to the grinding wheel successively forsharpening. To locate the individual teeth in the proper position ofrotation there is provided a tooth rest 23 mounted for universalmovement and adjustment about a. rod 24 which in turn is pivoted in amember 25 slidably adjustable on a member .26 fixed with the "supportill, the member 23 being clampable in any position of its adjustment byany suitable means such as the bolts and nuts shown.

\ ly movable supports as follows: Slidably guided on base II formovement in a direction at right angles to the path of support 9 is asupport 21 upon which a support 28 is slidably guided for movement in apath at right angles to the move- 55 Abrasive wheel unit 3 includesvarious relative- 50 ment of support 21. Pivoted on support 28 formovement about a.horizontal axis on a pivot pin 29 is a grinding wheelspindle carrier or support 30. The support 21 may be moved by a handwheel 3| fixed on a screw 32 engaging a nut 33 and may be clamped in anyposition of adjustment by the means of a screw 34 operating similarly tothe clamp screw l4. The support 28 may be reciprocated by a hand wheel36 fixed on a shaft 31 upon which is also fixed a spiral pinion 38engaging a rack 39 on the lower surface of the support 28, as shown inFig. 3. It is. this hand wheel 36 which is normally used for traversingthe grinding wheel 8 relative to the cutter mounted on spindle 4. Thesupport 30 may be manually shifted about the pivot 29 by grasping thesupport and shifting it bodily, but for fine adjustments there is.provided supplemental adjusting means best shown in Fig. 2 including ascrew member 48 pivoted on a bolt or stud 4| fixed in the support 36 andwhich works in an arcuate slot 42 in the support 28. Screw 48 isthreaded and is provided with a handnut 43 bearing on an ear or lug '44fixed with sup-. port 28. As the hand nut 43 is turned the. support 30is moved in the one or the other direction about pivot 29. Support 30may be clamped in any position of its pivotal adjustment by a nut 45 onthe stud 4|, a similar clamp stud 46 and nut 41 being provided at theother side of the support. This improved supporting structure forms thesubject matter of a co-pending application of Frank W. Curtis, SerialNo. 748,630, filed October 17, 1934.

The support 30 is formed in two pieces, there being a main portion ormember 48 and a removably attached motor housing portion or member 49.The portion 48 carries a front antifriction bearing 58 and anintermediate antifriction bearing 5|. The portion 49 carries a rearanti-friction bearing-52. The front bearing 58 includes an inner race 53shouldered against an enlarged portion of spindle 6 at 54, an outer race55 shouldered against the support member 48 at 56, there being aplurality of interposed anti-friction ball elements 51, the bearingbeing adapted to restrain both rearward axial and lateral movements ofthe spindle. The intermediate bearing 5| includes an inner race 58 whichis slidably fitted to spindle 6, an outer race 59 which is shoulderedagainst support member 48 at 68, and a plurality of interposedantifriction ball elements 6|, this bearing being adapted to restrainboth forward axial and lateral movements of the spindle. The inner race58 may be adjusted along spindle 6 by the means of a nut 62 threaded onthe spindle and the form of the various races and interposedanti-friction ball elements of the bearings 50, 5| is such thatadjustment of nut 62 serves to remove all slack in both these bearingsand thereby to fix the spindle 6 against axial movement in eitherdirection and against lateral movement at either end. A slight furthertightening of nut 62 sets up an initial or preloaded condition of eachof the bearings 50 and 5|, which serves to minimize or prevent anydisplacement of the spindle as the grinding load increases or decreasesand to prevent chatter or vibration of the grinding wheel.

The rear bearing 52 includes an inner-race 63 in which the spindle 6 isslidably fitted, an outer race 64 carried by the support portion 49, andinterposed anti-friction ball elements 65. This bearing prevents lateraldisplacement or whip- Ding of the rear end of the spindle 6.

A'fiywheel or inertia member 66 is fixed on spindle Gfat a point betweenbearings 58 and 5|. It is a wellknown fact that a grinding wheel whichis kept at-proper speed and which is prevented from either-torsional orlateral vibration or chatter will cut sharply and cleanly and with butlittle wear of the wheel.-, A relatively slight reduction in wheelspeed, suchas is ordinarily caused by the grinding wheel meeting thecutter tooth, or a relatively slight amount of vibration or chatter,will, on the other hand,- result in relatively very rapid wear of thegrinding wheel. particularly when the cutter blades being ground are ofextremely dense and resistant material, such, for instance, as tungstencarbide. The form and location of the member 66, relative to thegrinding wheel, the driving motor and the spindle bearings, has beenfound to very materially improve the action of the grinding wheel and toreduce the wear of the wheel to such extent that, even for cuttershaving a large number of teeth of the very hardest materials, the teethmay all be finish ground at one setting of the wheel, while stillmaintaining all the teeth of uniform size, thereby avoiding measuringthe individual teeth to insure uniformity.

A spindle brake generally denoted by numeral 61 may be used for quicklystopping the spindle. Brake 61 includes an arcuate member 68 best shownin Fig. 2 having a pivot 69 supported from the member 48. A brake bandsegment 18 is fixed on member 68 in a position to frictionally engagethe periphery of flywheel 66. A hand operable button member H isconnected to the member 68 by a plunger member l2-and serves to permitthe operator to engage the brake and quickly stop rotation of spindle 6when desired, the brake being normally held disengaged by a spring I3.

The power for rotation of spindle 6 is derived from a power motor whichmay be of any suitable form or type including a rotor member I4 which isfixed on spindle 6 at a point between the intermediate bearing 5| andthe rear bearing 52. The motor stator element 15 is fixed with thesupport portion 49 in manner to be removed to expose the rotor when theportion 49 is removed. The position and relationship of the motormembers relative to the grinding wheel, flywheel and spindle bearingshas also been found to be of material bearings, and drive means for saidwheel spindle including a power motor having a rotating portion fixedwith said wheel spindle and positioned axially between two of saidbearings.

2. In a cutter-grinder, the combination of a base, a cutter spindle anda grinding wheel spindle each rotatably supported from said base foradjustment of the one spindle relative to the other, a grinding wheelfixed on said wheel spindle at the front end thereof, bearings forsaidwheel spindle including a front anti-friction anaemia bearingadjacent said grinding wheel and adapted to resist axial thrust of saidspindle in the direction of the other end thereof and to resist lateraldisplacement of the front end thereof, a rear anti-friction bearingadjacent the-other end of said spindle and adapted to resist lateraldisplacement of said other end, and. an intermediate anti-frictionbearing adapted to resist axial thrust of said spindle in the otherdirection and to resist lateral displacement of the spindle portionsintermediate the ends thereof.

3. In a cutter grinder, the combination of a base, a cutter spindle anda grinding wheel spindle each rotatably supported from said base foradjustment ofthe one spindle relative to the other, a grinding wheelfixed on said wheel spindle at the front end thereof, bearings for saidwheel spindle including a front anti-friction bearing adjacent saidgrinding wheel and adapted to resist axial thrust of said spindle in thedirection of said other end and to resist lateral displacement of saidfront end, a rear anti-friction bearing adjacent said other end of saidspindle and adapted to resist lateral displace ment of said other end,and an intermediate anti-friction bearing adapted to resist axial thrustof said spindle in the other direction and to resist lateraldisplacement of the spindle portions intermediate the ends thereof, andmeans for initially preloading said front and intermediate bearings. I

4. In a cutter grinder, the combination of a base, a cutter spindle anda grinding wheel spindle each rotatably supported from said base foradjustment of the one spindle relative to the other, a grinding wheelfixed on said wheel spindle at the front end thereof, bearings for saidwheel spindle including a front anti-friction bearing adjacent saidgrinding wheel and adapted to resist axial thrust of said spindle in thedirection of the other end thereof and to resist lateral displacement ofsaid front end, a rear anti-friction bearing adjacent said other end ofsaid spindle and adapted to resist lateral displacement of said otherend, and an intermediate anti-friction bearing adapted to resist axialthrust of said spindle in the other direction and to resist lateraldisplacement of the spindle portions intermediate the ends thereof, anddrive means for said wheel spindle including a power motor providing arotor fixed with said spindle and axially between two of said bearings.

5. In a cutter grinder, the combination of a base, a cutter spindle anda grinding wheel spindle each rotatably supported from said base foradjustment of the one spindle relative to the other, a grinding wheelfixed on said wheel spindle at the front end thereof, bearings for saidwheel spindle including a front anti-friction bearing adjacent saidgrinding wheel and adapted to resist axial thrust of said spindle in thedirection of the other end thereof and to resist lateral displacement ofsaid front end, a rear anti-friction bearing adjacent said other end ofsaid spindle and adapted to resist lateral displacement of said otherend, and an intermediate anti-friction bearing adapted to resist axialthrust of said spindle in the other direction and to resist lateraldisplacement of the spindle portions intermediate the ends thereof, aflywheel fixed with said wheel spindle axially between said front andintermediate bearings, and drive other, a plurality of bearings for saidwheel spindle and spaced apart in the direction of the spindle axis, agrinding wheel fixed at the one end of said wheel spindle and axiallyoutside said bearings, a flywheel fixed to said wheel spindle betweensaid bearings, and a spindle brake including a brake member frictionallyengageable with the periphery of said flywheel.

7. A grinder for precision work, comprising a grinding spindle, agrinding wheel secured to one end of said spindle for rotation thereby,an antifriction bearing disposed on said spindle closely adjacent tosaid grinding wheel and adapted to support said spindle radially and inmanner to resist thrust axially in direction from said wheel toward saidbearing, a flywheel secured to said spindle closely adjacent to saidbearing at the side thereof opposite from said grinding wheel, a secondanti-friction bearing disposed on said spindle closely adjacent to saidflywheel at the side thereof opposite from said first bearing, saidsecond bearing being adapted to support said spindle radially andinmanner to resist thrust axially in direction toward said grinding wheel,means connected to said spindle at the side of. said second bearingopposite from said flywheel for driving said spindle, and means on saidspindle adapted for tightening said anti-friction bearings against eachother in manner to preload them to efiect rigid support of said spindle.

'8: A grinder for precision work, comprising a grinding spindle, agrinding wheel secured to one end of said spindle for rotationtherewith, an anti-friction bearing disposed on said spindle andoperative to support said spindle radially and in manner to resistthrust exerted axially in direction from said grinding wheel, a flywheelsecured to said spindle closely adjacent to said bearing at the sidethereof opposite from said grinding wheel, a second anti-frictionbearing disposed on said spindle closely adjacent to the other side ofsaid flywheel and operative to support said spindle radially and inmanner to resist thrust exerted axially in direction toward saidgrinding wheel, means on said spindle operative to tighten saidanti-friction bearings against each other in manner to preload them toeffect rigid support of said spindle, and means operatively connected tosaid spindle for rotating it.

